WASHINGTON -- A top aide to President Obama said it's possible that Obama could be impeached by the Republican-controlled House of Representatives.

House Speaker John Boehner's decision to proceed with a lawsuit against the president has "opened the door" to the third presidential impeachment in the nation's history, Senior Adviser Dan Pfeiffer told reporters at a Friday breakfast sponsored by the Christian Science Monitor.

"Impeachment is a very serious thing that has been bandied about by the recent Republican vice presidential nominee and others in a very un-serious way," he said, referring to former Alaska governor Sarah Palin. "We take it very seriously and I don't think it would be a good thing."

Pfeiffer was quick to add that "no one has alleged anything that is even six universes from what is generally considered" to be an impeachable offense.

Boehner has dismissed calls for Obama to be impeached. His spokesman, Michael Steel, called Pfeiffer's comments "a fundraising exercise for Democrats."

"We have a humanitarian crisis at our border, and the White House is making matters worse with inattention and mixed signals," Steel said. "It is telling, and sad, that a senior White House official is focused on political games, rather than helping these kids and securing the border."

Later, White House Press Secretary Josh Earnest said "prominent voices in the Republican party" have called for impeachment, but was hard-pressed to name one other than Palin. "I think there are some Republicans, including some Republicans that are running for office, hoping that they can get into office so they can impeach the president," he said.

A CNN/ORC poll released Friday shows 35% of Americans favor impeachment, which is about the same support for efforts to impeach Presidents Clinton and George W. Bush. Pfeiffer noted that a majority of Republicans -- 57% -- favor impeaching Obama.

Impeachment is the bringing of charges against a president or federal judge by the House of Representatives. A president can only be removed after a trial on those charges by the Senate.

Boehner has chosen a less drastic approach with a plan to sue Obama over his decision to delay enforcement of a provision in the Affordable Care Act requiring employers to provide health insurance. That plan passed the House Rules Committee Thursday, clearing the way for a vote on the House floor.

Pfeiffer said the lawsuit won't have an impact on how the president uses his executive authority. In fact, he said, the threat of lawsuits validates that Obama's executive actions are "far from the small ball that some have accused it of being."